The present invention is directed towards the production of a tire component. More specifically, the present invention is a method of forming a precured innerliner in such a manner to facilitate later splicing and curing of the innerliner during the bladderless manufacture of a tire.
To better understand the advantages and improvements achieved with the present invention, a brief discussion of tire construction and building procedures follows. A pneumatic tire is typically constructed by applying various components, or plies of the tire as flat stock, upon a rotating tire building drum to form a hollow, toroidal shaped green or uncured tire. The order of applying the components is as follows: first, an innerliner is wrapped upon the tire building drum; the innerliner is followed by carcass plies containing tire reinforcement, the carcass plies are followed (not necessarily in the following order) by the beads, apexes, chafers, sidewalls, belts and tread. The components are then expanded and formed into a toroidal shaped, green tire assembly, in a manner well known in the art. The green tire assembly is then removed from the tire building drum and placed into a shaping and vulcanizing mold having the shape of the finished tire.
In the conventional manner, the mold is sealed and the toroidal shaped green tire assembly is heated and expanded radially outward into the mold periphery by injecting pressurized gas or fluid into a curing bladder mounted within the mold and disposed within the green tire assembly. As the curing bladder expands, it forces the tread and sidewalls of the green tire assembly into contact with the heated mold walls to shape and vulcanize the green tire assembly into a fully vulcanized tire. During the radial expansion of the green tire assembly within the shaping and vulcanizing mold, the toroidally shaped plies expand radially outward to dimensions beyond those of the original green tire assembly. Therefore, the bladder is usually made of an expandable elastomeric material, such as butyl rubber, which also provides resistance to the steam or hot water used to force the tire against the mold surface.
During the production of tires on an assembly line, the curing bladder within the shaping and vulcanizing mold periodically wears out or fails. The tire industry has tried to eliminate the need for a curing bladder used in tire production. U.S. Pat. No. 4,166,883 discloses a method of forming a cured tire in a mold without a bladder. Instead of a bladder, the liner functions as the impervious layer. The liner is cured or partially cured to produce a steam- and water-resistant surface before the remainder of the tire is cured in a mold. The curing or partial curing is accomplished by electron irradiation. When partially curing is desired, the entire liner is cured to a desired depth. PCT publication WO 9609161A1 discloses forming a tire by pre-vulcanizing the normal hot vapor during vulcanization.
U.S. Pat. No. 3,027,289 also discloses a method of forming a tire without the use of a building bladder during the cure cycle. In forming the tire, a strip of elastomeric material is formed into an annular band by overlapping the ends of the strip by one-fourth of an inch and then curing only the overlapped portions. U.S. Pat. No. 3,027,289 is silent about any partial precuring of the elastomeric material.
The present invention is directed toward an improved preparation method of forming a tire innerliner. The tire innerliner so formed is best suited for use in the formation of a pneumatic tire in a bladderless curing system.
The present invention is directed toward an improved method of manufacturing a pneumatic tire using a bladderless curing system. The tire is built on an associated tire building drum by the layering of tire multiple tire components on the drum; one of the components is an innerliner strip. In accordance with the disclosed invention, the innerliner strip is formed with precured regions. The precured regions are formed by curing the innerliner strip at one or more regions intermediate of the ends of the strip. The strip is applied to the tire building drum and the ends are spliced and cured to one another.
In one aspect of the present invention, the innerliner strip is formed a continuous strip of elastomeric material wherein the continuous strip is uncured at predetermined locations. The continuous strip is then cut to form an innerliner strip with intermediate precured regions. The uncured predetermined locations may extend across the width of the continuous strip, at any angle relative to the lateral edge of the continuous strip. The uncured predetermined locations may also be located along the lateral edges of the continuous strip.
In another aspect of the invention, when the uncured predetermined location extends across the width of the continuous strip, the predetermined uncured location has a width in accordance with the following equation equal to two hundred percent or less of the value of the following equation: 1=t/tan (xcex2); wherein l=minimum length of the predetermined uncured location, t=average thickness of the continuous strip, and xcex2=the predetermined cutting angle.
Also disclosed is a pneumatic tire formed in a bladderless cure assembly. The tire is formed on an associated building drum by the layering of multiple tire components wherein one component is an innerliner strip. The innerliner strip is formed with precured regions. The precured regions are formed by curing the innerliner strip at one or more regions intermediate of the ends of the strip. The strip is applied to the tire building drum and the ends are spliced to one another. to one another.
In another aspect of the disclosed pneumatic tire, the innerliner splice extends at a radial angle across the inner surface of the tire.